Anisotropic growth of gold clusters to gold nanocubes under UV irradiation

A chiral reagent, 2-naphthol, has been introduced under alkaline solution as a reductant for HAuCl4 in CTAB micelle to produce exclusively cubic gold nanoparticles under UV photoactivation. Prolonged irradiation helped the digestion of the primarily evolved spherical particles into smaller gold nanocubes, which then act as tiny cubic seeds, leading to the formation of larger nanocubes. The smaller cubes take the assistance of CTAB under alkaline condition to serve as the seed in directing the transformation of all the spherical colloids into cubic shapes under continuous irradiation via Ostwald ripening. The shape transformation of the nanoparticles has been monitored by repetitive TEM imaging and absorption spectral analysis. The FTIR analysis proves that the gold nanocubes are capped by CTAB. The XRD pattern authenticates the formation of the fcc gold nanocubes. GCMS studies in turn confirmed the presence of hydroxylation of 2-naphthol in the course of the reaction, leaving exclusively cubic gold nanoparticles at the final stage of the photoactivation reaction.